There are known cleaning apparatuses (cf., for example, FR 2 567 552, FR 2 584 442, etc.) which comprise a hollow body; one or more device(s) for guiding and driving said hollow body over the immersed surface; and a pumping device which drives a pumping member such as a propeller which generates a flow of liquid between at least one liquid inlet and at least one liquid outlet of the hollow body, and through a filtration chamber.
Some known apparatuses have one or more member(s) which protrude(s) from their base towards the immersed surface. The protruding members, when they are not motors, may have varied functions such as friction for the purposes of cleaning the immersed surface, guiding and/or confinement of the liquid towards the liquid inlet of the apparatus, etcetera. EP 1 290 293 provides an example of such apparatuses.
When such apparatuses which have at least one non-motorized member which protrudes from the base thereof have a limited driving power, the problem arises of such a protruding member, and therefore the apparatus, becoming blocked on obstacles at the base, such as bottom plugs or changes of gradient.
It is desirable to provide these apparatuses with a drive power which is as low as possible in order to reduce their energy consumption and their production cost, in particular in apparatuses which are provided with a drive device of the electric motor type which is on-board the hollow body. The same problem occurs in the case of an apparatus with hydraulic propulsion (by means of reflux or suction), if the flow of liquid (which it is desirable to reduce for economic purposes) is not sufficiently great to provide the drive power required to overcome some obstacles.
Furthermore, the protruding portions of such an apparatus are capable of damaging the coatings of fragile surfaces, such as swimming pool liners, in particular at locations where the liners have obstacles or surface irregularities, such as folds, for example.